1. Field of the Invention
The present invention relates to a thermoplastic resin composition having a pearly luster prepared by mixing polymethyl methacrylate (hereinafter, "PMMA") and a styrene-acrylonitrile copolymer (hereinafter, "AS resin") and, more particularly, it relates to a thermoplastic resin composition having a pearly luster comprising the AS resin in specific proportions and with the AS resin having a particular acrylonitrile content.
The invention relates further to a thermoplastic resin composition having a pearly luster comprising the above-mentioned resin composition having glass fibers added thereto.
Still further, the invention relates to a thermoplastic resin composition having a pearly luster comprising the above described mixture of PMMA and the AS resin and additionally an acrylonitrile-butadiene-styrene resin (hereinafter, "ABS resin").
2. Description of the Prior Art
For providing a thermoplastic resin with a pearly luster, a method is known wherein scaly flakes, basic lead carbonate, a mica pearling agent, etc., is dispersed by kneading in the resin (for example, as disclosed in Japanese Patent Publication No. 12,174/'73). However, the use of these pearling agents as described above is accompanied by difficulties in that the resin is discolored by the extent of kneading of the pearling agent or by heating at processing or the pearly luster appearance is superficial and a so-called deep pearly effect is not obtained since the pearling agent appears only on the surface of the resin at molding or shaping the resin.
On the other hand, an attempt to use a polycarbonate as a material for providing a pearly luster as described in, for example, Japanese Patent Publication Nos. 12,284/'73 and 16,063/'72, an attempt to mix a methacrylic resin, the AS resin, and a styrene resin as described in Japanese Patent Publication No. 38,700/'71, and an attempt to mix an acrylic resin and a styrol resin as described in Japanese Patent Publication No. 30,909/'72 have been recently proposed. However, the attempt to employ a polycarbonate is accompanied by the disadvantages that polycarbonate itself is expensive and although the resin composition has an excellent mechanical strength, the molding conditions are restricted, while the attempt to simply mix acrylic resin and a styrol resin does not provide high strength. Furthermore, in mixing a methacrylic resin, AS resin, and styrene resin, the components are difficult to mix uniformly, the mechanical strength becomes weak depending on their mixing ratio, and further a peeling phenomenon depending on the mixing ratio and the molding conditions tends to occur with this resin composition.
As another example, a mixture of a polyacrylic resin, a polyamide resin or a denatured rubber-like polymer, and a polystyrene resin has been proposed as described in Japanese Patent Publication No. 34,907/'71 but, although such a resin may exhibit a pearly effect, the resin has poor mechanical strength (an Izod impact value of about 1.0-1.6 Kg.-cm./cm.sup.2) and thus such a resin cannot be used for purposes requiring high mechanical strength such as, for example, as a hinge for a cosmetic container, e.g., a powder compact, etc., or the resin composition does not exhibit a good pearly effect according to the mixing ratio of the resin components.